Certain joint offsets lead to "NameError: global name 'sqrt' is not defined" in calc_base_parms() #10

import sympy
import sympybotics
rbtdef = sympybotics.RobotDef('left_arm',
                         [('pi/2', 0, 0, 'pi/2'),
                         ('pi/2', 0.03, 0.246, '-pi'),
                         ('-pi/2', -0.03, 0, '-pi/4'),
                         ('pi/2', 0, 0.186, 'pi'),
                         ('pi/2', 0, 0, 'pi'),
                         ('pi', 0, 0, 'pi/2')],
                        dh_convention='standard'
                         )
rbt = sympybotics.RobotDynCode(rbtdef, verbose=True)
rbt.calc_base_parms(verbose=True)

import sympy
import sympybotics
rbtdef = sympybotics.RobotDef('left_arm',
                         [('pi/2', 0, 0, '-pi/2'),
                         ('pi/2', 0.03, 0.246, '-pi/2'),
                         ('-pi/2', -0.03, 0,' 0'),
                         ('pi/2', 0, 0.186, '0'),
                         ('pi/2', 0, 0, 'pi'),
                         ('pi', 0, 0, 'pi/2')],
                         dh_convention='standard'
                         )
rbt = sympybotics.RobotDynCode(rbtdef, verbose=True)
rbt.calc_base_parms(verbose=True)

generating geometric model
generating kinematic model
generating inverse dynamics code
generating gravity term code
generating coriolis term code
generating coriolis matrix code
generating inertia matrix code
generating regressor matrix code
done
calculating base parameters and regressor code
---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
/usr/lib/python2.7/dist-packages/IPython/utils/py3compat.pyc in execfile(fname, *where)
    202             else:
    203                 filename = fname
--> 204             __builtin__.execfile(filename, *where)

/home/philipp/thor_identification/left_arm/URDF_file_handling/dh_to_baseparams.py in        <module>()
     17 rbt = sympybotics.RobotDynCode(rbtdef, verbose=True)
     18 
---> 19 rbt.calc_base_parms(verbose=True)
     20 print rbt.dyn.baseparms
     21 

/usr/local/lib/python2.7/dist-packages/sympybotics-1.0_dev-py2.7.egg/sympybotics            /robotmodel.pyc in calc_base_parms(self, verbose)
    120             _fprint('calculating base parameters and regressor code')
    121 
--> 122         self.dyn.calc_base_parms(regressor_func)
    123 
    124         H_se = Subexprs()

/usr/local/lib/python2.7/dist-packages/sympybotics-1.0_dev-py2.7.egg/sympybotics/dynamics   /dynamics.pyc in calc_base_parms(self, regressor_func)
     53 
     54         Pb, Pd, Kd = find_dyn_parm_deps(
---> 55             self.dof, self.n_dynparms, regressor_func)
     56 
     57         self.Pb = sympy.Matrix(Pb).applyfunc(lambda x: x.nsimplify())

/usr/local/lib/python2.7/dist-packages/sympybotics-1.0_dev-py2.7.egg/sympybotics/dynamics   /dyn_parm_dep.pyc in find_dyn_parm_deps(dof, parm_num, regressor_func)
     20                for j in range(dof)]
     21         Z[i * dof: i * dof + dof, :] = numpy.matrix(
---> 22             regressor_func(q, dq, ddq)).reshape(dof, parm_num)
     23 
     24     R1_diag = numpy.linalg.qr(Z, mode='economic').diagonal().round(round)

/usr/local/lib/python2.7/dist-packages/sympybotics-1.0_dev-py2.7.egg/sympybotics            /robotmodel.pyc in regressor_func(q, dq, ddq)

NameError: global name 'sqrt' is not defined